Various types of electrical equipment, such arc resistant switchgears, are usually designed to withstand the pressures and temperatures of gases associated with an internal arcing fault. Enclosures of such equipment are designed to direct pressure and hot arc byproducts away from human personnel.
The occurrence of arcing inside electrical switchgears has many undesirable results. Conductors and arc surrounding material are vaporized and converted to plasma by the arc energy during the event. The massive rate of expansion of the plasma causes a sudden pressure increase inside the enclosure of the switchgear, resulting in severe mechanical and thermal stress on the equipment and its components. As a result of the high pressures generated, door/cover, hinges and latching means of the equipment are placed under significant stress. If the door/cover, hinges and latching means should yield and/or deform, personnel in vicinity of the equipment would be exposed to dangerous levels of energy. In other words, the ionized gases associated with arcing faults may be released at pressures and temperatures sufficient to damage the switchgear equipment and potentially cause deadly harm to anyone in close proximity.
A commonly employed method for improving the enclosures of a switchgear in the event of arcing faults is to provide arc-resistant switchgears that meets switchgear standards, with a means for venting gases from the compartment in which an arcing fault occurs. These compartments are designed to withstand the pressures and temperatures of the gases associated with an arcing fault and reduce the likelihood or extent of damage to the switchgear.
Other prior art solutions include exhaust chambers or plenums which channel exhaust products such as hot gases, debris, and metal parts away from the room where the arcing electrical equipment and handling personnel are located. Usually a plenum assembly is provided on top of the switchgear so that the hot gases flow out through the plenum and further through a duct to a space outside the building.